1. Field of the Invention
The present invention relates to a method and an apparatus for mounting a plurality of circuit components on a circuit substrate and thereby producing an electric circuit.
2. Related Art Statement
It is practiced to test, when an electric circuit (xe2x80x9cECxe2x80x9d) is produced by mounting a plurality of circuit components (xe2x80x9cCCsxe2x80x9d) on a circuit substrate (xe2x80x9cCSxe2x80x9d), a state in which the CCs are mounted on the CS. For example, it is judged whether one or more CCs have not been mounted on a CS, and/or whether a position where a CC is mounted on a CS, or an attitude taken by a CC mounted on a CS is not appropriate. This test may be performed after CCs are temporarily fixed to a CS with an adhesive, a solder paste, or the like, or after the CCs are finally fixed to the CS by hardening the adhesive, soldering the solder paste, or the like. In the former case, even if the test shows that one or more CCs have not been mounted, or have not been appropriately mounted, on a CS, the CCs can be finally fixed to the CS after an operator removes those problems. Thus, the yield of good electric circuits is improved. Alternatively, the operator can discard one or more CSs for which some problem relating to the mounting of one or more CCs thereon has been found. Thus, no useless, finally fixing operation is performed. In addition, it is possible to identify a position error of a CC which is produced in a temporarily fixing operation, from that produced in a finally fixing operation. In the last case, the operator can take appropriate measures against each of those problems.
However, in the conventional manner, a test after a temporarily fixing operation is performed after all CCs are mounted on a CS. Hence, it is required to dispose a testing device between a CC mounting device which temporarily fixes the CCs to the CS, and a finally fixing device such as a hardening furnace which finally fixes the CCs to the CS. This leads to increasing the overall length of an EC assembly line and the cost of the same.
It is therefore an object of the present invention to provide a circuit-component mounting method and a circuit-component mounting system each of which is free from the above-identified disadvantage.
The present invention provides a circuit-component mounting method and a circuit-component mounting system which have one or more of the technical features which are described below in respective paragraphs given parenthesized sequential numbers (1) to (16). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed.
(1) According to a first feature of the present invention, there is provided a method of mounting a plurality of circuit components on a circuit substrate for producing an electric circuit, comprising the step of testing, each time one of the circuit components is mounted on the circuit substrate, a state in which said one circuit component is mounted on the circuit substrate. The test result may show that one circuit component (xe2x80x9cCCxe2x80x9d) has not been mounted, or has not been appropriately mounted, on the circuit substrate (xe2x80x9cCSxe2x80x9d). In the present CC mounting method, each time one of the CCs is mounted on the CS, a state in which said one CC is mounted on the CS is tested. This test step may be carried out each time one CC is temporarily fixed to the CS. Since the present method does not require that a testing device be provided between a CC mounting device and a finally fixing device, neither the overall length of an electric-circuit (xe2x80x9cECxe2x80x9d) assembly line nor the cost of the same is increased.
(2) According to a second feature of the present invention, there is provided a system for mounting a plurality of circuit components on a circuit substrate, comprising, a substrate supporting device which supports the circuit substrate; a component mounting device which mounts each of the circuit components on the circuit substrate supported by the substrate supporting device; a testing device which tests an actual state in which the each circuit component is mounted on the circuit substrate by the component mounting device; and a control device which controls the component mounting device to mount the each of the circuit components on the circuit substrate and controls the testing device to test, each time one of the circuit components is mounted on the circuit substrate by the component mounting device, an actual state in which the one circuit component is mounted on the circuit substrate. In the present CC mounting system, the control device controls the mounting device to mount each of the CCs on the CS, and controls the testing device to test, each time one of the CCs is mounted on the CS by the mounting device, an actual state in which said one CC is mounted on the CS. Accordingly, the present CC mounting system may be employed for carrying out the CC mounting method according to the first feature (1). It is preferred that the testing device be one which can identify whether a position where each CC is mounted on the CS and an attitude taken by each CC mounted on the CS are appropriate. However, the testing device may be one which can identify only whether a position where each CC is mounted on the CS is appropriate, or one which can identify only whether each CC has not been mounted on the CS. Regarding the CC-position test, in particular, it is preferred to test not only (a) a position or positions of a reference point (e.g., center point) of each CC in one or two directions parallel to a surface of the CS but also (b) a position of the same in a direction perpendicular to the CS surface. However, it is possible to test only either one of the above two sorts of positions (a), (b). In the case of the position or positions (a), it is preferred to test two positions of the reference point of each CC in two directions which perpendicularly intersect each other in a plane parallel to the CS surface. Regarding the CC-attitude test, it is preferred to test not only (c) an angle of inclination of a reference line (e.g., center axis line) of each CC with respect to a direction parallel to the CS surface but also (d) an angle of inclination of the reference line with respect to a direction perpendicular to the CS surface. However, it is possible to test only either one of the above two sorts of positions (c), (d). The position error (b) and attitude (angle) error (d) of each CC with respect to the direction perpendicular to the CS surface result from the xe2x80x9cunfixedxe2x80x9d state of said each CC on the CS surface. A CC may erroneously take an upright attitude, i.e., lie on its one side. This can be said as a 90-degree inclination of the CC with respect to the direction perpendicular to the CS surface.
(3) According to a third feature of the present invention which includes the second feature (2), the testing device comprises an image taking device which takes an image of at least a portion of the each circuit component mounted on the circuit substrate; and judging means for judging whether the actual state of the each circuit component is appropriate, by comparing, with a reference state of the each circuit component, the actual state thereof determined based on the image taken by the image taking device. Testing the state in which each CC is mounted on the CS involves detecting said each CC. The detection of each CC may be carried out by a contact-type detector, but a non-contact-type detector is preferable to the contact-type detector. Of various sorts of non-contact-type detectors, an optical detector that can detect an object at a high speed is preferable, and an image taking device is particularly preferable since it can easily obtain various sorts of information. The image taking device is advantageously provided by a surface-image taking device such as a CCD (charge-coupled device) camera, but may be provided by a line-image taking device such as a line sensor. The actual state of each CC may be indicated in terms of any of the various states and amounts exemplified in the context of the CC mounting system according to the second feature (2), and the reference state of each CC may be indicated in terms of the same. In addition, the reference state of each CC may be a standard state in which the CC is ideally mounted on the CS; a boundary state in which the CC is mounted on the CS with the largest tolerable error; or a cautious state in which the CC is mounted on the CS with a large tolerable error which may lead to the boundary state and accordingly need an appropriate action to reduce the error. In the case where the reference state is the standard state, the testing device may judge whether the actual state of each CC is appropriate, based on whether the difference between the actual state and the standard state is large or not. In the case where the reference state is the boundary or cautious state, the testing device may judge whether the actual state of each CC is appropriate, based on whether the actual state goes beyond the boundary or cautious state or not.
(4) According to a fourth feature of the present invention which includes the third feature (3), the testing device additionally comprises a slit-light emitting device which emits a slit light along a plane which is inclined with respect to a surface of the circuit substrate and intersects a surface of the each circuit component mounted on the surface of the circuit substrate, and wherein the image taking device takes an image of at least an area of the surface of the each circuit component which area is exposed to the slit light emitted by the slit-light emitting device. The testing device may not only judge whether each CC is present or absent on the CS, but also determine a position where each CC is mounted on the CS and/or an attitude taken by each CC mounted on the CS. For a certain reason, e.g., the reason that the surface of the CS is much darker than that of each CC, it may be difficult to take an image of an area of the surface of the CS which area is exposed to the slit light. Even in this case, it is possible to test the presence or absence of each CC on the CS, the position of each CC on the CS and/or the attitude of each CC on the CS, based on only the image of the area of the surface of each CC which area is exposed to the slit light. However, in the case where the testing device can take both of the above two images, the testing device can easily determine the position and attitude of each CC with respect to the direction perpendicular to the CS surface. In addition, since the present CC mounting system uses the image or images of only a small area or areas, it can a process image data representing those image or images in a short time. Thus, the present system can mount each CC on the CS at a short interval of time, while reliably testing the actual state in which said each CC is mounted on the CS.
(5) According to a fifth feature of the present invention which includes the fourth feature (4), the slit-light emitting device comprises a plural-slit-lights emitting device which emits a plurality of slit lights along a plurality of planes, respectively, which are parallel to each other.
(6) According to a sixth feature of the present invention which includes the fourth or fifth feature (4) or (5), the slit-light emitting device comprises two slit-light emitters which emit respective slit lights parallel to respective directions which are inclined with respect to the surface of the circuit substrate in respective planes which are perpendicular to each other and each of which is perpendicular to the surface of the circuit substrate, so that the respective slit lights emitted by the two slit-light emitters substantially perpendicularly intersect each other on the surface of the each circuit component mounted on the surface of the circuit substrate.
(7) According to a seventh feature of the present invention which includes any one of the second to sixth features (6), the circuit-component mounting system further comprises a memory which stores data indicating the each circuit component, when the testing device provides a test result that the actual state of the each circuit component is not appropriate; and a test-result output device which outputs, after all the circuit components are mounted on the circuit substrate, the data stored in the memory, so that an operator can recognize the each circuit component indicated by the data outputted by the test-result output device. In the present CC mounting system, even if it is found during a CC mounting operation that one or more CCs have not been mounted, or have been inappropriately mounted, on the CS, the CC mounting operation is continued without being interrupted and, after all the CCs to be mounted on the CS are actually mounted on the CS, the test-result output device is operated to output the data stored in the memory. In the case where the testing device finds the inappropriate mounting of at least one CC on the CS, it is desirable that when the output device outputs the data, stopping means which may be provided by a portion of the control device be operated for automatically stopping the operation of the CC mounting device. The test-result output device may be an optical display device such as a liquid crystal display or a cathode ray tube display, or a printer which records the test result on a sheet of paper. In either case, when the output device outputs the test result after the CC mounting operation, the operator can recognize the CC or CCs which has or have not been mounted, or has or have inappropriately mounted, on the CS and can take appropriate measures against those problems. For example, in the case where a certain CC has not been mounted on the CC, the operator can manually mount the CC on the CS; and in the case where a CC is mounted on the CS with an excessively great position error, the operator can correct the position of the CC on the CS and then place the CS on the following device such as another CC mounting device, an adhesive hardening device, a solder reflowing surface, or the like. Alternatively, based on the test result outputted by the output device, the operator can adjust, for preventing the re-occurrence of the same sort of inappropriate CC mounting, the CC mounting device, or a control panel or a controllable section of an adhesive applying device or a solder-paste applying device which is provided on an upstream side of the CC mounting device in the direction in which the CS is conveyed.
(8) According to an eighth feature of the present invention which includes the seventh feature (7), the circuit-component mounting system further comprises candidate specifying means for specifying at least one candidate for a cause of the test result that the actual state of the each circuit component is not appropriate, wherein the test-result output device comprises a candidate output device which outputs the candidate specified by the candidate specifying means.
(9) According to a ninth feature of the present invention which includes the eighth feature (8), the testing device further comprises information obtaining means for obtaining information relating to a component-mount position where the each circuit component is mounted on the circuit substrate, and wherein the candidate specifying means comprises component-mount-position-dependent candidate specifying means for specifying the candidate by taking into account the information obtained by the information obtaining means. There are candidates which can be specified based on the information relating to the component-mount position where each CC is mounted on the CS. Those candidates may include the amount or amounts of difference (i.e., distance or distances) between the actual position or positions of each CC mounted on the CS and the correct position or positions of each CC, and the direction or directions of difference of the former position or positions from the latter position or positions. The actual position or positions of each CC are an example of the above-described actual state of each CC, and the correct position or positions of each CC are an example of the above-described reference state of each CC.
(10) According to a tenth feature of the present invention which includes the eighth or ninth feature (8) or (9), the circuit-component mounting system further comprises a temporarily-fixing-material applying device which is provided on an upstream side of the component mounting device in a direction of conveying of the circuit substrate and which applies, to a component-mount place on a surface of the circuit substrate, a temporarily fixing material which temporarily and stably fixes the each circuit component to the component-mount place, wherein the candidate specifying means comprises applied-material-state testing means for testing a state in which the temporarily fixing material is applied by the temporarily-fixing-material applying device to the component-mount place on the surface of the circuit substrate; and applied-material-state-dependent candidate specifying means for specifying the candidate by taking into account the state of the temporarily fixing material tested by the applied-material-state testing means. The state of the temporarily fixing material tested by the applied-material-state testing means may include at least one of an amount and a position of the applied temporarily fixing material. If the temporarily fixing material is not appropriately applied to the CS, each CC may not be appropriately mounted on the CS.
(11) According to an eleventh feature of the present invention which includes any one of the second to tenth features (2) to (10), the circuit-component mounting system comprises a controllable device which is controllable for preventing the circuit components from being inappropriately mounted on the circuit substrate; and a controllable-device control device which controls the controllable device based on the actual state of the each circuit component tested by the testing device. In the present circuit-component mounting system, the controllable-device control device controls the controllable device to carry out automatically the operation or operations which should be carried out by the operator based on the circuit component or components indicated by the data outputted by the test-result output device in accordance with the seventh feature (7). Although the present system does not essentially need the test-result output device, it is preferred that the present system include not only the controllable device and the controllable-device control device but also the test-result output device. In the case where the controllable-device control device starts controlling the controllable device when the error of the position where a CC is mounted on a CS or the attitude taken by a CC mounted on a CS exceeds a permissible range or limit, the present system effectively prevents the return or re-occurrence of inappropriate mounting of a CC or CCs on a CS or CSs. In the case where the controllable-device control device starts controlling the controllable device when the error of the position where a CC is mounted on a CS or the attitude taken by a CC mounted on a CS exceeds a threshold range or value narrower or smaller than the permissible range or limit, the present system surely prevents the occurrence of inappropriate mounting of a CC or CCs on a CS or CSs beyond the permissible range or limit. The control device of the CC mounting system in accordance with the second feature (2) may comprise (a) automatically stopping means for automatically stopping the component mounting device when the error of the position where a CC is mounted on a CS or the attitude taken by a CC mounted on a CS exceeds a permissible range or limit; and (b) an operable member which is operable by the operator for re-starting the component mounting device after he or she has carried out a necessary operation or operations.
(12) According to a twelfth feature of the present invention which includes the eleventh feature (11), the component mounting device comprises at least one component holder which holds the each circuit component, and a holder moving device which moves the component holder to a desired position in a holder-conveying plane parallel to a surface of the circuit substrate supported by the substrate supporting device, and wherein the controllable device comprises the holder moving device. For example, the component holder may be one which includes a suction pipe which sucks and holds a CC by applying a negative pressure thereto. In this case, if the suction pipe is not straight, i.e., includes a bent portion, the CC held thereby would have X-direction- and/or Y-direction-position errors if the suction pipe is rotated about its axis line for changing the angular or rotation position of the CC according to a control program, or correcting the rotation-position error of the CC. The greater the degree of bending of the suction pipe or the angle of rotation of the suction pipe is, the greater the X-direction- and/or Y-direction-position errors are. Since the degree of bending of the suction pipe can be estimated based on the past data indicative of the X-direction- and/or Y-direction-position errors of CCs, and the rotation position of each CC at the time when it is mounted on a CS can be obtained from the control program, the holder moving device can be controlled to move the component holder by corrected X-direction and/or Y-direction distances which minimize the X-direction- and/or Y-direction-position errors of each CC. Thus, the holder moving device corresponds to the controllable device which is controllable for preventing a CC from being inappropriately mounted on a CS.
(13) According to a thirteenth feature of the present invention which includes the eleventh or twelfth feature (11) or (12), the circuit-component mounting system further comprises a temporarily-fixing-material applying device which is provided on an upstream side of the component mounting device in a direction of conveying of the circuit substrate and which applies, to a component-mount place on a surface of the circuit substrate, a temporarily fixing material which temporarily and stably fixes the each circuit component to the component-mount place, wherein the controllable device comprises the temporarily-fixing-material applying device.
(14) According to a fourteenth feature of the present invention which includes the thirteenth feature (13), the temporarily-fixing-material applying device comprises a adhesive dispenser including a syringe in which an adhesive as the temporarily fixing material is stored; a nozzle connected to the syringe; and a pressurized-gas supplying device which supplies a pressurized gas to the syringe for causing an amount of the adhesive to be released from the nozzle so that a spot of the adhesive is formed on the surface of the circuit substrate, wherein the controllable device comprises an adjusting device which adjusts at least one of the amount of the adhesive dispensed by the adhesive dispenser and a position where the adhesive is dispensed by the adhesive dispenser. In this case, the adjusting device comprises at least one of (a) an adhesive-amount adjusting device which adjusts the amount of the adhesive dispensed by the adhesive dispenser and (b) an adhesive-dispensing-position adjusting device which adjusts a position where the adhesive is dispensed by the adhesive dispenser.
(15) According to a fifteenth feature of the present invention which includes the thirteenth feature (13), the temporarily-fixing-material applying device comprises a screen printing device including a screen having a plurality of holes at a plurality of positions, respectively, which correspond to a plurality of positions on the surface of the circuit substrate where a solder paste as the temporarily fixing material is to be applied; and a squeegee which applies, through the screen, the solder paste to the surface of the circuit substrate, and wherein the controllable device comprises an adjusting device which adjusts at least one of an amount of the solder paste applied by the screen printing device and a position where the solder paste is applied by the screen printing device. In this case, the adjusting device includes at least one of (a) a solder-paste-amount adjusting device which adjusts an amount of the solder paste applied by the screen printing device and (b) a solder-paste-applying-position adjusting device which adjusts a position where the solder paste is applied by the screen printing device. It is usual that the solder paste has a high viscosity immediately after CCs are mounted on a CS. Thus, the solder paste functions as the temporarily fixing material which temporarily fixes the CCs to the CS.
(16) According to a sixteenth feature of the present invention which includes any one of the second to fifteenth features (2) to (15), the component mounting device comprises a plurality of component holders which are revolvable around a common axis line; and a holder revolving device which revolves the holders around the common axis line and stops each of the holders at at least one predetermined stop position, wherein the substrate supporting device comprises a substrate moving device which moves the circuit substrate in a direction parallel to a surface of the circuit substrate, so that a component-mount place on the surface of the circuit substrate is positioned at a component mounting position corresponding to the predetermined stop position, and wherein the testing device comprises an image taking device which takes an image of at least a portion of the each circuit component mounted on the circuit substrate and which is fixed at a position, near the component mounting position, where the image taking device can take the image of the portion of the each circuit component. The holder revolving device may be one which essentially includes an intermittently rotatable body which holds a plurality of component holders in a peripheral portion thereof such that the component holders are equiangularly spaced from each other about an axis line thereof, and which is intermittently rotatable about the axis line such that it is continuously rotated by a predetermined intermittent-rotation angle in a first step and then is stopped in a second step and the first and second steps are repeated. Alternatively, the holder revolving device may be one which is disclosed in U.S. patent application Ser. No. 08/769,700 assigned to the Assignee of the present U.S. patent application, that is, one which includes a plurality of rotary members which holds a plurality of component holders, respectively, and which are rotated about a common axis, independent of each other. The present CC mounting system can mount each CC on a CS at a shortened interval of time, that is, with an improved efficiency. In addition, the image taking device need not be moved, i.e., can be fixed. In the case where the image taking device is iteratively moved and stopped together with the component holder which is moved while holding the CC, it is difficult to increase the speed of movement of the image taking device because the image taking device has a considerably great mass and accordingly it is difficult to improve the efficiency of mounting of CCs. In contrast, the present CC mounting system is equipped with the fixed image taking device, which leads to improving easily the efficiency of mounting of CCs.